Introduction : Gamithromycin has both bacteriostatic and bactericidal action, mediated through the disruption of bacterial protein synthesis. The broad spectrum antimicrobial activity of gamithromycin includes Mannheimia haemolytica, Pasteurella multocida and Histophilus somni, the bacterial pathogens most commonly associated with Bovine Respiratory Disease (BRD). The benefits of Zactran are the efficacy of a single dose of 1 ml/25 kg for the treatment and prevention of BRD, demonstrated by the improvement of the clinical signs of the disease. Also, the efficacy of gamithromycin was demonstrated as comparable to that of an already approved veterinary medicinal product containing tulathromycin. The most common side effect is a transient local swelling at the injection site consistent with the macrolide class of antimicrobials.